The subject invention is in the field of electrical switches, switching systems and overload protection devices. In particular, it is in the field of apparatus for disconnecting an electrical system from one source of power and connecting it to another and vice versa, a primary example being disconnecting the electrical system of a building from the electrical utility power supply and connecting to an auxiliary generator power supply.
Apparatus for disconnecting an electrical system from one source of power and connecting it to another, and vice versa, is widely used in boats, home, factories, hospitals and the like. In the majority of installations of such switching, the switching is implemented by adding wiring and switches to the electrical power system. However, installations which incorporate an electrical utility meter which is plugged into a receptacle offer the possibility of implementing the power supply switching with a minimum of wiring. The control apparatus disclosed in U.S. Pat. No. 3,654,484, issued Apr. 4, 1972 to Jorgensen et al., is an example of power supply switching which takes advantage of the possibility. The Jorgensen et al. apparatus plugs into the utility meter plug and the utility meter is plugged into the apparatus. The apparatus comprises a receptacle for plugging in a connector from an auxiliary power supply and a switch which connects the electrical system to either the utility power supply or the auxiliary power supply. The Jorgensen et al. apparatus was marketed by the Onan Corporation under size and costs constraints which rendered the apparatus economically and practically feasible. However, because of these restraints, the switching in the Onan product did not meet utility standards in terms of safety, reliability, longevity and overload protection.
The present invention is directed to an apparatus that meets these needs and other shortcomings in the prior art.
The subject invention is a power transfer device that plugs into a power meter receptacle. The device may further comprise a power meter or a receptacle for a power meter. Utility system power flows into the device from the power meter receptacle (box). It also comprises a receptacle for plugging in an alternate or auxiliary power supply. Electrical conductors, preferably bus bars, conduct power from the utility systems through the meter and into the served system or from the auxiliary power socket into the served system. The device also comprises switches for connecting one or the other power supply to the served electrical system. In a preferred embodiment, the switches are commercially available circuit breakers. The invention can also be implemented using switches and overload protection devices, such as fuses.
A mechanism is provided for operating both switches in unison and may allow an off position in which neither switch is on.